Photographic silver halide emulsion having an increased sensitivity and reduced fogging

ABSTRACT

The sensitivity of light-sensitive photographic silver halide emulsions can be increased and the fogging can be decreased if the chemical ripening of that emulsions is performed in the presence of mercapto alkyl quaternary salts or acetothioalkyl quaternary salts of the following formula WHEREIN R represents alkyl with up to six carbon atoms; two R radicals of the same nitrogen can be combined to form a heterocyclic ring; R&#39;&#39; represents alkyl with up to six carbon atoms, which can be substituted, or an aralkyl group; R&#39;&#39;&#39;&#39; represent H or -CO-CH3; n is one to six; and X is any anion.

United States Patent [72] Inventors I-larald Huckstadt Cologne; WilhelmSaleck, Schildgen; August Randolph, Leverkusen; Franz Moll, Leverkusen;Anita Von Koenig, Leverkusen, all of Germany [21] Appl. No. 883,606

[22] Filed Dec. 9, 1969 [45] Patented Oct. 26, 1971 [73] AssigneeAgta-Gevaert Aktiengesellschalt Leve'rltusen, Germany [32] Priority Dec.23, 1968 [33] Germany [54] PHOTOGRAPHIC SILVER HALIDE EMULSION HAVING ANINCREASED SENSITIVITY AND REDUCED FOGGING 11 Claims, No Drawings [52][1.8. 96/663, 96/107,96/109 [51] Int. Cl. G03c 5/24, G030 1/28,G03c 1/34[50] Field of Search 96/663,

[56] References Cited UNl'l'ED STATES PATENTS 3,453,281 7/1969Burnessetal 3,471,296 10/1969 l-luckstadtetal Primary Examiner-Norman G.Torchin Assistant Examiner-Richard E. Fichter Attorney-Connolly and HutzABSTRACT: The sensitivity of light-sensitive photographic silver halideemulsions can be increased and the fogging can be decreased if thechemical ripening of that emulsions is performed in the presence ofmercapto alkyl quaternary salts or acetothioalkyl quaternary salts ofthe following formula PI-IOTOGRAPIIIC SILVER IIALIDE EMULSION HAVING ANINCREASED SENSITIVITY AND REDUCED FOGGING The present invention relatesto a process for increasing the sensitivity of photographic silverhalide emulsions together with reduced fogging by the addition ofmercaptoalkyl quaternary salts or acetothioalkyl quaternary salts.

The sensitivity of a photographic emulsion can be effected in two ways.First the sensitivity can be increased during the preparation of theemulsion at the stage of so-called chemical ripening, by increasing theripening time or by the addition of suitable compounds such asthiosulfate or other additives which usually contain sulfur. The othermethod of increasing the sensitivity of photographic emulsion consistsof adding socalled development accelerators or chemical sensitizers.These are usually added to the finished ripened emulsion.

Development accelerators which have been described for this purposeinclude, e.g., compounds which have an onium structure (such asquaternary ammonium and phosphonium and ternary sulfonium salts), andalso polyalkylene oxides and polyalkylene oxide derivatives are veryfrequently employed.

Nearly all the additives, however, have the unfavorable side effect ofincreasing the fogging of the emulsion. In order to counteract theincrease in fogging which may occur not only during storage in theheating cupboard but also in the fresh sample, it is in most casesnecessary to increase the quantity of stabilizer. However, it is aproperty of most stabilizers that they reduce the sensitivity when usedin substantial quantities.

In this way the effect of thedevelopment accelerator may be impaired.

There is, therefore, an urgent need to find development accelerators orripening agents which do not bring about any additional increase infogging and there is also an urgent need to find stabilizers which donot reduce the sensitivity of the photographic emulsion. It is desirableto find substances which would both increase the sensitivity of thephotographic emulsion and which would stabilize the fogging.

This is the object of the present invention.

It has now been found that silver halide emulsions which have increasedsensitivity and reduced fogging are obtained by adding to the emulsions,in the course of after ripening, mercaptoalkyl quaternary salts oracetothioalkyl quaternary salts of the following general formula:

wherein represents:

R an alkyl group having up to six carbon atoms; two R radicals attachedto the same nitrogen atom may, with this nitrogen atom, form a saturatedfive-, six-, or sevenmembered heterocyclic ring, which may containfurther hereto atoms, e.g. a piperidine, morpholine, thiomorpholine,pyrrolidine, or hexamethyleneimine ring or an unsaturated heterocyclicring such as pyridine, in the latter case R is not present;

R an alkyl group having up to six carbon atoms which may be substituted,for example haloalkyl, hydroxyalkyl, cyanoalkyl, carboxyalkyl or anaralkyl group such as benzyl or phenylethyl, the aryl radical of whichmay be substituted in turn, e.g. with alkyl, alkoxy, halogen, and aminogroups;

n represents an integer of from 1 to 6;

X any anion such as chloride or bromide, tosylate, perchlorate orsulfate, when R contains a carboxylate group. X is absent.

The following formula are given for the purpose of illustrating thecompounds more fully but are not intended to restrict the scope of theinvention:

The compounds according to the invention are prepared according to thefollowing reaction scheme:

These reactions have been described in respect of open chainedquaternary salts in Archiv der Pharmazie 293, 55-57 (1960); and inLiebig's Ann. 630, 105-155 (1960). The cyclic salts are prepared inanalogous manner.

The compounds according to the invention show their advantageous effectparticularly clearly when they are used in place of thiosulfate or otherconventional sulfur ripening agents for chemical ripening. Apart fromthe increase in sensitivity described in the example, the considerablereduced fogging in the samples is very noticeable. This reduction infogging can be seen not only in fresh samples but also after storage ina heating cupboard.

The advantage of using the compounds according to the invention lies notso much in the increase in sensitivity, which is to be regarded as onlyaverage, but in the combination of increase in sensitivity withreduction in fogging which enables other ingredients, which may possiblyincrease the fogging to be added to the emulsion without the totalfogging then being too great.

Emulsion prepared with the substances according to the invention will,therefore, be particularly suitable for use in combination with otherdevelopment accelerators. The reduced fogging will also be veryimportant in the preparation of color emulsions, since these arenormally particularly susceptible to fogging.

The cause for the above-mentioned effect of mercapto quaternary saltsand acetothioquaternary salts isstill not clear. Their mode of action isvery similar to that of disulfide quater nary salts (see U.S. Pat.Application Ser. No. 886,039, filed Dec. 17, 1969 (A-G 442) except thatthey have no positive effect when added as casting additives to thefinished ripened emulsion, although they do not reduce the sensitivitynor cause fogging as often can be observed when mercapto compounds areadded to an emulsion.

The compounds do not have any advantageous effect when used in thedeveloper.

It is desirable to add the compounds according to the invention to thephotographic emulsion at the start of chemical ripening. The quantityadded depends on the emulsion used in a particular case and can easilybe determined by those skilled in the art at any time by the usualtests.

A quantity of 0.001 to 0.3g. per mol of silver halide will generally besufficient.

The substances according to the invention can be used in any silverhalide emulsions. Suitable silver halides are silver chloride, silverbromide or mixtures thereof, optionally with a small silver iodidecontent of up to 10 mols percent. Silver halides may be dispersed in theusual hydropholic compounds, for example carboxymethylcellulose,polyvinyl alcohol, polyvinyl pyrrolidone, alginic acid and its salts,esters or amides or preferable gelatin.

The emulsions may also contain other chemical sensitizers, e.g.quaternary ammonium and phosphonium salts and ternary sulfonium salts,reducing agents as stannous salts, polyamines such as diethylenetriamine or sulfur compounds as described in U.S. Pat. No. 1,574,844.The above-mentioned emulsions may also contain salts of noble metalssuch as ruthenium, rhodium, palladium, iridium, platinum or gold forchemical sensitization, as described in the article by R. Koslowsky, Z.Wiss. Phot. 46, 65-72 (1951).

The emulsions may be optically sensitized, e.g. with the usualpolymethine dyes such as neutrocyanines, basic or acid carbocyanines,rhodacyanines, hemicyanines, styryl dyes, and oxonols. Sensitizers ofthis type have been described in the book by F. M. Hamer The CyanineDyes and Related Compounds" 1964). i

The emulsion may contain the usual stabilizers, e.g. homopolar orsalt-type compounds of mercury containing aromatic or heterocyclic rings(for example of mercaptotrazoles), simple mercury salts, sulfoniummercury double salts and other mercury compounds. Azaindenes, especiallytetraor pentaazaindenes, and in particular those which are substitutedwith hydroxyl or amino groups, are also suitable for use as stabilizers.Compounds of this type are described in the article by Birr, Z. Wiss.Phot. 47, 2-58 (1952). Other suitable stabilizers include heterocyclicmercapto compounds, e.g. phenylmercapto tetrazole. quaternarybenzothiazole derivatives and benzotriazole.

The emulsions may be hardened in the usual manner, for example withformaldehyde or halogenated aldehydes which contain a carboxyl group,such as mucobromic acid, diketones, methane sulfonic acid esters, anddialdehydes.

The emulsions treated with the mercaptoalkyl and S-acetylthio-alkylquaternarysalts according to the invention may also contain colorcouplers for the production of color photographic images.

EXAMPLE 1 A silver iodobromide emulsion containing 5 mols percent ofsilver iodide is prepared in the usual manner. For after-ripening, thepAg is adjusted to 8.9. the pH to 6.8. and the viscosity to 8 cp. Goldthiocyanate is then added and the emulsion is divided into 7 equalparts. The following additives are then added to the individual samples(the amounts given are based on 1 kg. of emulsion containing l30 g. ofsilver halide:

Sample A: Comparison sample without additive Sample B: 3.3 mg.ofCompound V Sample C: 3.3 mg. ofCompound Xlll Sample D: 7.0 mg.ofCompound lV Sample :3.3 mg. ofCompound XV Sample 3.3 mg. ofCompound VISample G: 3.3 mg. of a compound of the following formula (forcomparison) The after-ripening is carried out to maximum sensitivity andthe samples are made ready for casting by the addition of 600 mg. ofsaponin as wetting agent, 200 mg. of 4-hydroxy-6- methyl-l,3,3a,7-tetraazaindene as stabilizer and 10 ml. ofa l0 percent aqueoussolution of formaldehyde as hardener, per kg. ofemulsion.

The samples are then cast on cellulose acetate, exposed in asensitometer behind a grey step wedge and developed for minutes in adeveloper of the following composition:

A difference of 3 represents a difference of one shutter stop.

A comparison of samples F and G shows that the mercapto quaternary saltsare very similar in their effect to the disulfide quaternary salts,which is easily understandable on chemical grounds.

Example 2 An emulsion as in example 1 is divided into 8 equal parts.

The following substances are added per kg. of emulsion to the individualparts: Sample A: Comparison sample-without additive Sample B: 3.3 mg.ofCompound 1X Sample C: 3.3 mg. ofCompound Vlll Sample D: 3.3 mg.ofCompoundl Sample E: 3.3 mg. ofCompound 11 Sample F: 3.3 mg. ofCompoundXVI Sample G: 3.3 mg. ofCompound XVll Sample 1-1: 3.3 mg. ofCompound XIVThe samples are cast, exposed and developed as in example 1.

Table 2 Sample Sensitivity y fog log 3 days 60 A Blank 0.82 0.19 0.24 B+l.2 0.87 0.13 0.18 C +l.l 0.84 0.12 0.16 D +0.7 0.83 0.16 0.18 E +0.9"0.86 0.15 0.18 F +l.0 0.85 0.12 0.15 O +l.l 0.84 0.12 0.16 H +0.9 0.860.13 0.16

LII

A difference of 3 represents a difference of one shutter stop.

We claim:

1. A light-sensitive photographic material having at least one silverhalide emulsion layer which contains a compound ofthe following formulaas ripening agent:

in which R represents an alkyl group having up to six carbon atoms; twoR radicals attached to the same nitrogen atom may with the said nitrogenatom form a saturated five-, sixor seven-membered heterocyclic ringcontaining at least one hetero atom or an unsaturated heterocyclic ring,in the latter case R is not present;

R represents an alkyl group having up to six carbon atoms, which may besubstituted or an aralkyl group, the aryl radicals of which may besubstituted;

R" represents H or COCH n is an integer offrom l to 6;

X 9 is any anion; when R contains a carboxylate group, X e

is absent.

2. A light-sensitive photographic material according to claim 1, whereinthe silver halide emulsion layer in addition contains color couplers.

3. A light-sensitive photographic material according to claim 1, whichcontains a compound of the following formula:

CH3 CH I 3CH CH CH;SH 0104 4. A light-sensitive photographic materialaccording to claim 1, which contains a compound of the followingformula:

5. A light-sensitive photographic material according to 6. Alight-sensitive photographic material according to claim 1, whichcontains a compound of the following formula:

7. A light-sensitive photographic material according to claim 1, whichcontains a compound ofthe following formula:

8. A light-sensitive photographic material according to claim 1, whichcontains a compound of the following formula:

9. In the process for the production of black-and-white or 11. In theprocess for the preparation of photographic silver color images bydeveloping an imagewise exposed light-sensihalide emulsions byprecipitating the silver halide in the tive photographic material whichcomprises at least one silver presence of a protective colloid, washingand chemical ripenhalide emulsion layer, the improvement according towhich ing the improvement according to which the chemical ripenthedevelopment is carried out in the presence of a compound ing is carriedout in the presence of a compound of the followof the following'formula:ing formula:

R represents an alkyl group having up to six carbon atoms;

two R radicals attached to the same nitrogen atom may with the saidnitrogen atom form a saturated five-, sixor R represents an alkyl grouphaving up to six carbon atoms; two R radicals attached to the samenitrogen atom may seven-membered heterocyclic ring containing at leastone with the Said t g atom form a 531i ated -i hetero atom or anunsaturated heterocyclic ring, in the seven-membered heterocyclic ringcontaining at least one latter case R is notpresent; hetero atom or anunsaturated heterocyclic ring, in the R represents an alkyl group havingup to six carbon atoms, ialtef Case is not P which y Substituted alkylgroup, the y R represents an alkyl group having up to six carbon atoms,:adlcais Ofwhlch y be substituted; which may be substituted or anaralkyl group, the aryl rePfesems H :1 radicals ofwhich may besubstituted; n is an integer offrom l to 6; R t H CO CH X e is anyanion; when R contains a carboxylate group, X repfesfll s or is absent nis an integer offrom l to 6; 10. The process according to claim 9,wherein the exposed is y anion; when Contains a yiate gro p, Xphotographic material is developed with a color'forming i5absemdeveloper in the presence of color couplers.

2. A light-sensitive photographic material according to claim 1, whereinthe silver halide emulsion layer in addition contains color couplers. 3.A light-sensitive photographic material according to claim 1, whichcontains a compound of the following formula:
 4. A light-sensitivephotographic material according to claim 1, which contains a compound ofthe following formula:
 5. A light-sensitive photographic materialaccording to claim 1, which contains a compound of the followingformula:
 6. A light-sensitive photographic material according to claim1, which contains a compound of the following formula:
 7. Alight-sensitive photographic material according to claim 1, whichcontains a compound of the following formula:
 8. A light-sensitivephotographic material according to claim 1, which contains a compound ofthe following formula:
 9. In the process for the production ofblack-and-white or color images by developing an imagewise exposedlight-sensitive photographic material which comprises at least onesilver halide emulsion layer, the improvement according to which thedevelopment is carried out in the presence of a compound of thefollowing formula: in which R represents an alkyl group having up to sixcarbon atoms; two R radicals attached to the same nitrogen atom may withthe said nitrogen atom form a saturated five-, six- or seven-memberedheterocyclic ring containing at least one hetero atom or an unsaturatedheterocyclic ring, in the latter case R'' is not present; R'' representsan alkyl group having up to six carbon atoms, which may be substitutedor an aralkyl group, the aryl radicals of which may be substituted;R'''' represents H or -CO-CH3; n is an integer of from 1 to 6; X is anyanion; when R'' contains a carboxylate group, X is absent.
 10. Theprocess according to claim 9, wherein the exposed photographic materialis developed with a color-forming developer in the presence of colorcouplers.
 11. In the process for the preparation of photographic silverhalide emulsions by precipitating the silver halide in the presence of aprotective colloid, washing and chemical ripening the improvementaccording to which the chemical ripening is carried out in the presenceof a compound of the following formula: in which R represents an alkylgroup having up to six carbon atoms; two R radicals attached to the samenitrogen atom may with the said nitrogen atom form a saturated five-,six- or seven-membered heterocyclic ring containing at least one heteroatom or an unsaturated heterocyclic ring, in the latter case R'' is notpresent; R'' represents an alkyl group having up to six carbon atoms,which may be substituted or an aralkyl group, the aryl radicals of whichmay be substituted; R'''' represents H or -CO-CH3; n is an integer offrom 1 to 6; X is any anion; when R'' contains a carboxylate group, X isabsent.